Plants, when stressed by parasites, various infections, ultraviolet radiation, or injury, synthesize specialized polyphenol compounds called phytoalexins. Resveratrol, a potent phytoalexin, was originally identified in 1940 from the white hellebore lily. The most concentrated known natural source is red wine, and the Asian medicinal plant Polygonum cuspidatum (Giant or Japanese Knotweed). Resveratrol, together with other bioactive ingredients in these plants, has been used as a botanical dietary supplement in herbal formulations for thousands of years in traditional Chinese, Japanese, and Indian medicine for their health producing effects.

In the human diet the greatest source of resveratrol and associated polyphenols comes from the skins of red grapes. Resveratrol acts as the plant”s “antibiotic” or fungicide to ward off attacks, particularly from various fungi. During wine making, the resveratrol is concentrated. The type of grape, climate, and soil are all factors that influence the level of resveratrol found in red wine. The longer the red grape skin is in contact with the wine and juice, the higher the resveratrol content. Resveratrol itself is an off-white powder that is chemically is found in two forms, depending on the structure of the molecule. Trans-resveratrol is the more active form (as compared to cis-resveratrol), preferred for use in supplements. It is relatively stable if protected from light, oxygen, and a high pH environment. If exposed to light, it will rapidly convert to the less stable form, and lose much of its biological effect. Dried red grape skins yield approximately 92 mg of resveratrol from 1 kg of grape skins, which is approximately a 10,000:1 ratio.